Your sales report says MXN 180,000. The bank received MXN 164,000. Issued CFDI total MXN 171,000. None of those figures has to be wrong. The difference may come from credit sales, collections from an earlier month, refunds, bank fees, or invoices still waiting to be issued.
Use one exception list
Keep a short list of transactions that could not be matched to a CFDI, bank movement, customer, supplier or business purpose. Assign each item an owner and a resolution date. A visible exception list keeps small differences from becoming permanent balances and makes the monthly close easier to repeat.
The monthly close should explain those differences. Start with the sales report, identify which customers paid and match those payments to invoices and bank records. You should be able to see how each total was calculated and which transactions still need an explanation.
What a monthly close should produce
A small business does not need a finance department to close the month. It needs a repeatable set of records, a named owner for each task, and a short list of unresolved items.
The finished close should show:
- sales made, invoices issued, and cash collected;
- customer balances still outstanding;
- expenses incurred, supplier invoices received, and amounts paid;
- every bank movement matched to a business transaction;
- owner deposits, withdrawals, loans, and reimbursements identified separately;
- the tax figures sent to the accountant and the returns later filed;
- exceptions that remain open, with a person and due date assigned.
If two deposits remain unidentified, record their amounts and assign someone to investigate. Ask the accountant whether they affect a return that is due. Moving them into "other income" without checking their source can give the wrong tax result.
Build six records and keep them connected
| Record | Minimum fields | Monthly test |
|---|---|---|
| Sales register | Date, customer, amount, VAT treatment, payment status, CFDI UUID | Sales system agrees with invoices after documented timing differences |
| Accounts receivable | Invoice, due date, original amount, collections, balance | Customer balances add up to unpaid sales |
| Bank ledger | Date, bank description, amount, matched transaction, reviewer | Statement ending balance agrees with the reconciled ledger |
| Expense and payable register | Supplier, purpose, CFDI, payment date, payment method, balance | Paid and unpaid expenses are separated |
| Tax workpaper | CFDI, collections, payments, VAT, withholding, adjustments | Figures sent to the accountant tie back to records |
| Owner transaction log | Date, owner, amount, reason, agreement or receipt | Personal and business movements are not mixed |
One spreadsheet can hold several of these records at first. The format matters less than stable columns, one person responsible for updates, and a locked copy after the month closes.
Reconcile operations, CFDI, and the bank
Three systems describe different moments:
- the sales system records what the business sold;
- CFDI records what the business invoiced;
- the bank records cash movement.
List the timing differences and adjustments that explain why the totals differ. Do not change a total just to match another report.
For sales, start with the operating report. Add sales from a prior period invoiced this month and subtract current sales still awaiting invoice. The result should explain issued CFDI, after cancellations, credit notes, and other documented adjustments.
For collections, start with opening accounts receivable. Add current credit sales and subtract customer payments. The result should equal closing accounts receivable. Then match each payment to the bank or another documented payment method.
| Difference | Likely explanation | Evidence to keep |
|---|---|---|
| Bank deposit with no current invoice | Collection of an older invoice, customer advance, loan, or owner contribution | Customer reference, agreement, prior CFDI, or corporate record |
| Invoice with no bank deposit | Credit sale, cash collection, offset, or wrong payment method | Receivable balance and collection terms |
| Sales report above CFDI total | Pending invoices, public-sales global CFDI, or timing error | Sales detail and invoicing schedule |
| CFDI total above sales report | Advance, duplicate invoice, replacement, or wrong period | Contract, cancellation trail, and related UUID |
| Bank withdrawal with no supplier invoice | Loan payment, tax, payroll, owner withdrawal, or unsupported expense | Statement, contract, receipt, or exception note |
Never resolve a difference by changing a description until the number looks familiar. Follow the transaction to its source.
Keep the XML and check each invoice's status
The XML is the tax record. A PDF is a readable representation, and a screenshot is weaker still. Download issued and received XML directly from your invoicing system or use the SAT's CFDI consultation and recovery service.
Your monthly archive should preserve:
- issued, received, payment, payroll, and withholding CFDI;
- current status of each relevant UUID;
- cancellation acknowledgments;
- replacement relationships between the old and new CFDI;
- payment supplements for PPD invoices;
- credit notes and the documents they affect.
When replacing a CFDI, the SAT's cancellation process requires cancellation reason 01 and the fiscal folio of the replacement. Keeping only the new PDF leaves half of that trail missing.
Record unsupported expenses without pretending they are deductible
A business may incur a real expense and still lack the documents needed for a tax deduction or VAT credit. The accounting record and the tax treatment are separate decisions.
Keep a list of missing documents with enough detail to follow up:
| Field | Example |
|---|---|
| Transaction | MXN 1,850 paid to a repair provider |
| Business reason | Emergency repair to delivery equipment |
| Available evidence | Bank transfer and service message |
| Missing item | Supplier CFDI |
| Owner | Operations manager |
| Deadline | Before the monthly tax handoff |
| Final treatment | CFDI received, nondeductible, reimbursed, or escalated |
Do not delete the expense because the CFDI is missing. Do not classify it as deductible merely because a receipt exists. Record the event, request the missing document, and let the accountant determine the tax treatment from the evidence and applicable rules.
Put cash and owner transactions under stricter rules
Cash creates gaps because the bank cannot show who paid, what was purchased, or whether change came back. Use a fixed petty-cash fund with:
- one custodian;
- an approved amount;
- numbered vouchers;
- receipts and CFDI when available;
- replenishment only after review;
- a count at month-end.
Owner transactions need their own log. A transfer from an owner may be capital, a loan, reimbursement, or payment for a sale. Those labels have different legal and tax effects. Write down the reason when the money moves and collect the agreement or corporate approval. Reconstructing intent six months later is expensive and rarely convincing.
Use a close calendar that fits the business
Agree on a date to send the records to your accountant, leaving time for questions and corrections before filing. This sample schedule can help you assign the work.
| Timing | Work | Person responsible |
|---|---|---|
| Every week | Match bank transactions, update collections, request missing CFDI | Bookkeeper or administrator |
| Last business day | Freeze the sales report, count cash, list uninvoiced sales | Operations and sales |
| First two business days | Download statements and CFDI, post final transactions | Administrator |
| Next two business days | Reconcile banks, receivables, payables, and owner accounts | Bookkeeper |
| After reconciliation | Prepare tax workpapers and exception list | Bookkeeper and accountant |
| After filing | Save returns, receipts, payment records, and final ledgers | Accountant and administrator |
Set internal dates according to the company's filing duties. The accountant should receive the package early enough to review it, ask questions, and correct documents before the statutory deadline.
What to send the accountant
Include an index when you send the monthly records. It helps the accountant find the files and see what is missing:
- bank statements and completed reconciliations;
- sales register and closing accounts receivable;
- expense register and closing accounts payable;
- issued, received, cancelled, and replacement CFDI;
- payroll totals and related payment evidence;
- tax payments, withholding, and notices received;
- owner transaction log and supporting agreements;
- exception list with amounts and questions.
Good questions name the transaction. "Can we deduct the MXN 18,400 laptop paid with the owner's card, and what reimbursement record is missing?" gives the accountant something to resolve. "Can we deduct electronics?" does not.
Software does not replace the controls
Buy software after defining the records and the close owner. A system helps when it:
- imports bank transactions without overwriting the original description;
- stores the UUID and XML with each transaction;
- separates preparation from approval;
- shows who changed a record and when;
- locks closed periods or requires approval to reopen them;
- exports the detail used in tax workpapers.
Automatic categorization is a draft. Someone still needs to decide whether "Transfer SPEI" is a customer payment, an owner loan, a supplier refund, or a transfer between company accounts.
Keep records long enough
Article 30 of Mexico's Federal Tax Code generally requires accounting and tax documentation to be kept for five years, counted under the rule in that article. Some corporate, capital, dividend, tax-loss, and long-running records must be kept longer.
Do not use a five-year automatic deletion rule for every file. Set a retention category when the document enters the archive, back up the archive, and test that someone other than the person who created it can restore a closed month.
Measure whether the close is improving
Track a few numbers:
- business day on which the close finished;
- count and value of unmatched bank transactions;
- customer invoices past due;
- supplier expenses waiting for CFDI;
- changes made after filing;
- difference between the first tax estimate and the filed amount.
Review whether the same questions keep returning. If supplier invoices are always missing, for example, ask for them when approving payment rather than waiting until the end of the month.
Where Fintax fits
Fintax can help organize the monthly close, reconcile CFDI with bank records and prepare the figures used for tax returns. Agree on which reports you will receive and how unresolved transactions will be explained.
Frequently asked questions
What is the minimum accounting a small business needs?
At minimum, keep a sales register, accounts receivable, bank reconciliation, expense and payable register, tax workpaper, and owner transaction log. The records must agree through documented differences.
Is a bank statement enough to support an expense?
No. It proves that money moved, but it does not by itself prove the business purpose, CFDI requirements, or tax treatment. Keep the invoice, agreement, receipt, approval, and other evidence that applies.
Should every difference be fixed before closing?
Every material difference should be explained or placed on an exception list with an owner and deadline. Hiding a difference in a generic account is not a fix.
How often should a small business reconcile its bank account?
Weekly review keeps the list manageable, and a full reconciliation should form part of every monthly close. Businesses with many daily transactions may need automated matching and more frequent review.
Official links to complete the task
Open official services from a new browser tab, confirm the taxpayer and period, and save the resulting acknowledgment or evidence with the case.
